1. Field of the Invention
The present invention relates to a solar cell and a manufacturing method thereof, and more specifically to a hybrid organic solar cell with perovskite structure as absorption material and a manufacturing method thereof.
2. Description of the Prior Art
In recent years, it has been spotlighted as a development of various renewable energies (e.g., solar cell, fuel cell, wind power generation, etc.) because large quantities of fossil fuel are consumed. For example, an organic polymer solar cell is an attractive renewable energy technology with their advantages of low cost, easy fabricating process, flexibility and portability. In addition, the organic polymer solar cell is continuously improved and developed by many researchers, so that the practicality of the organic polymer solar cell is gradually increased, for instance, the organic polymer solar cell can be assembled on a building or clothing. Therefore, the organic polymer solar cell even has the opportunity to replace a current solar cell using a semiconductor substrate.
For example, a traditional organic polymer solar cell is arranged by sandwiching with a glass substrate, a positive electrode layer made of indium tin oxide (ITO), a hole transport layer made of PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)), an absorptive active layer made of P3HT:PCBM (poly(3-hexylthiohene):(6,6)-phenyl C61 butyric acid methyl ester) hybrid system and a negative electrode layer made of aluminum. The principle of current generation of the traditional organic polymer solar cell is to produce an exciting phenomenon by using P3HT to absorb photons of sunlight, and to produce free electrons by potential difference between P3HT/PCBM interfaces, so that electron-hole pairs are separated. This is so-called transferring process of photo-induced charge. Holes generated by absorbing a light source in the structure of the absorptive active layer are collected in the positive electrode layer made of indium tin oxide (ITO) through a hole collection layer made of PEDOT:PSS having high penetration and work function which can be matched. Electrons are mostly collected in a negative electrode modified with aluminum, and then electrically connected to an external circuit, thereby generate a current. In another traditional organic polymer solar cell, the absorptive active layer can also be classified into two separate layers (i.e., a P3HT layer and a PCBM layer), and a heterojunction is existed between the separate layers. The principle of current generation of the traditional organic polymer solar cell is the same as that of above-mentioned principle.
Above P3HT is an organic polymer material with a moderate molecular weight (about 40˜60 KDa) and good carrier mobility, and incompatibility of PCBM, that will be able to form a good heterojunction, so that power conversion efficiency of the device is near 4% or greater than 4%. However, when a molecular weight of P3HT is too small, solution is hard to form a smooth film on the substrate, that is, molecules cannot be flatted efficiently on the entire surface of the substrate due to the small intermolecular force, so that the solution is condensed into small blocks, and it is difficult to form a complete film. Conversely, when a molecular weight is too large, thereby not only leads to poor solubility of the molecules in the solution, but also extent of phase separation of a heterojunction form of P3HT/PCBM is too obvious, thereby plunging carrier mobility thereof, and thus an effect for improving the power conversion efficiency of the device cannot be achieved. Therefore, when an absorption material of P3HT is manufactured, a size of molecular weight thereof must be strictly controlled. Furthermore, since P3HT is an organic polymer, and therefore a process required for organic synthesis thereof (e.g., a Grignard metathesis) is generally relatively more complex in comparison to a method for synthesizing an inorganic compound or small molecular organic compound, thereby equipment costs and processing costs required for synthesizing P3HT are relatively high, and thus advantageous to reduce the application for manufacturing and mass producing such the organic polymer solar cell.
Therefore, there is a need to provide a hybrid organic solar cell with perovskite structure as absorption material and a manufacturing method thereof, so as to overcome the disadvantage in the prior art.